TM 55-1510-222-10 auto   ignition   systems.      The   ARM   position   initiates   a readiness   mode   for   the   auto   ignition   system   of   the corresponding engine.  The system is disarmed when in the   OFF   position.      Each   circuit   is   protected   by   the corresponding   START   CONTR   #1   or   #2,   5-ampere circuit  breaker  on  the  overhead  circuit  breaker  panel (fig. 2-6). b.    Auto  Ignition  Annunciators.    If  an  armed  auto ignition system changes from a ready condition to an operating  condition  (energizing  the  igniter  plugs  in  the engine)  the  corresponding  engine's  green  annunciator will illuminate.  The annunciator is placarded #1 IGN ON or   #2   IGN   ON   and   indicates   that   the   igniters   are energized.  The auto ignition system is triggered from a ready  condition  to  an  operating  condition  when  engine torque   drops   below   approxi-mately   20%.      Therefore, when an auto ignition system is armed, the igniters will be   energized   continuously   during   the   time   when   an engine is operating at a level below approximately 20% torque.  The auto ignition annunciators are protected by the    5-ampere    IGNITOR    CONTR    #1    or    #2    circuit breakers,  located  in  the  overhead  circuit  breaker  panel (fig. 2-6). 2-30.  ENGINE STARTER-GENERATORS. One starter-generator is mounted on the accessory  drive  section  of  each  engine.    Each  starter- generator  is  able  to  function  either  as  a  starter  or  as  a generator. In the starter function, 28 volts DC is required to power rotation.  In the generator function, each unit is capable of 400-amperes DC output.  When the starting function  is  selected,  the  starter  control  circuit  receives power through the respective 5-ampere START CONTR circuit  breaker  on  the  overhead  circuit  breaker  panel from   either   the   aircraft   battery   or   an   external   power source.    When  the  generating  function  is  selected,  the starter-generator provides electrical power. 2-31.  ENGINE INSTRUMENTS. The   engine   instruments   are   arranged   vertically near the center of the instrument panel (fig. 2-14). a.  Turbine Gas Temperature Indicators.  The two TGT  gages  on  the  instrument  panel  are  calibrated  in degrees Celsius (fig. 2-14).  Each gage is connected to thermocouple  probes  located  in  the  hot  gases  between the turbine wheels.  The gages register the temperature present   between   the   compressor   turbine   and   power turbine for the corresponding engine. b.    Engine  Torquemeters.    The  two  torquemeters on  the  instrument  panel  indicate  torque  applied  to  the propeller  shafts  of  the  respective  engines  (fig.  2-14). Each  gage  shows  torque  in  percent  of  maximum  using two percent graduations and is actuated by an electrical signal  from  a  pressure  sensing  system  located  in  the respective propeller reduction gear case. The torquemeters   are   protected   by   individual   0.5-ampere circuit breakers placarded TORQUE METER #1 or #2 on the overhead circuit breaker panel (fig. 2-6). c.    Turbine  Tachometers.    The  two  tachometers on   the   instrument   panel   register   compressor   turbine RPM  (N.)  for  the  respective  engine  (fig.  2-14).    These indicators   register   turbine   RPM   as   a   percentage   of maximum   gas   generator   RPM.      Each   instrument   is slaved    to    a    tachometer    generator    attached    to    the respective engine. d.  Oil Pressure/Oil  Temperature  Indicators.    The two gages on the instrument panel register oil pressure in PSI and oil temperature in°  C (fig. 2-14).  Oil pressure is taken from the delivery side of the main oil pressure pump.      Warning   annunciators   placarded   No.      1   OIL PRESS   and   No.      2   OIL   PRESS   are   located   in   the warning annunciator panel.  Oil tem- perature  is  transmitted  by  a  thermal  sensor  unit  which senses   the   temperature   of   the   oil   as   it   leaves   the delivery  side  of  the  oil  pressure  pump.    Each  gage  is connected   to   pressure   and   temperature   transmitters installed on the respective engine.  Both instruments are protected  by  5-ampere  circuit  breakers,  placarded  OIL PRESS and OIL TEMP #1 or #2, on the overhead circuit breaker panel (fig. 2-6). e.    Fuel  Flow  Indicators.    The  two  gages  on  the instrument  panel  (fig.  2-14)  register  the  rate  of  flow  for consumed  fuel  as  measured  by  sensing  units  coupled into the fuel supply lines of the respective engines.  The fuel   flow   indicators   are   calibrated   in   increments   of hundreds    of    pounds    per    hour.        Both    circuits    are protected by 5-ampere circuit breakers placarded FUEL FLOW  #1  or  #2,  on  the  overhead  circuit  breaker  panel (fig. 2-6). 2-29